Publications
31 results found
Guo Z, Xu Z, Xie F, et al., 2023, Investigating the Superior Performance of Hard Carbon Anodes in Sodium-Ion Compared With Lithium- and Potassium-Ion Batteries, ADVANCED MATERIALS, ISSN: 0935-9648
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- Citations: 1
de Tomas C, Alabidun S, Chater L, et al., 2023, Doping carbon electrodes with sulfur achieves reversible sodium ion storage, JOURNAL OF PHYSICS-ENERGY, Vol: 5, ISSN: 2515-7655
Mercer MP, Nagarathinam M, Gavilan-Arriazu EM, et al., 2023, Sodiation energetics in pore size controlled hard carbons determined <i>via</i> entropy profiling, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 11, Pages: 6543-6555, ISSN: 2050-7488
Olsson E, Cottom J, Alptekin H, et al., 2022, Investigating the Role of Surface Roughness and Defects on EC Breakdown, as a Precursor to SEI Formation in Hard Carbon Sodium-Ion Battery Anodes, SMALL, Vol: 18, ISSN: 1613-6810
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- Citations: 1
Rubio N, Suter T, Rana Z, et al., 2022, Platinum deposition on functionalised graphene for corrosion resistant oxygen reduction electrodes, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 10, Pages: 20121-20127, ISSN: 2050-7488
Titirici M, Baird SG, Sparks TD, et al., 2022, The sustainable materials roadmap, Journal of Physics: Materials, Vol: 5, Pages: 1-98, ISSN: 2515-7639
Over the past 150 years, our ability to produce and transform engineered materials has been responsible for our current high standards of living, especially in developed economies. However, we must carefully think of the effects our addiction to creating and using materials at this fast rate will have on the future generations. The way we currently make and use materials detrimentally affects the planet Earth, creating many severe environmental problems. It affects the next generations by putting in danger the future of the economy, energy, and climate. We are at the point where something must drastically change, and it must change now. We must create more sustainable materials alternatives using natural raw materials and inspiration from nature while making sure not to deplete important resources, i.e. in competition with the food chain supply. We must use less materials, eliminate the use of toxic materials and create a circular materials economy where reuse and recycle are priorities. We must develop sustainable methods for materials recycling and encourage design for disassembly. We must look across the whole materials life cycle from raw resources till end of life and apply thorough life cycle assessments (LCAs) based on reliable and relevant data to quantify sustainability. We need to seriously start thinking of where our future materials will come from and how could we track them, given that we are confronted with resource scarcity and geographical constrains. This is particularly important for the development of new and sustainable energy technologies, key to our transition to net zero. Currently 'critical materials' are central components of sustainable energy systems because they are the best performing. A few examples include the permanent magnets based on rare earth metals (Dy, Nd, Pr) used in wind turbines, Li and Co in Li-ion batteries, Pt and Ir in fuel cells and electrolysers, Si in solar cells just to mention a few. These materials are classified as
Trotta F, Wang GJ, Guo Z, et al., 2022, A Comparative Techno-Economic and Lifecycle Analysis of Biomass-Derived Anode Materials for Lithium- and Sodium-Ion Batteries, ADVANCED SUSTAINABLE SYSTEMS, Vol: 6, ISSN: 2366-7486
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- Citations: 4
Au H, Crespo-Ribadeneyra M, Titirici M-M, 2022, Beyond Li-ion batteries: performance, materials diversification, and sustainability, ONE EARTH, Vol: 5, Pages: 207-211, ISSN: 2590-3330
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- Citations: 9
Alptekin H, Au H, Olsson E, et al., 2022, Elucidation of the Solid Electrolyte Interphase Formation Mechanism in Micro-Mesoporous Hard-Carbon Anodes, ADVANCED MATERIALS INTERFACES, Vol: 9, ISSN: 2196-7350
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- Citations: 12
Rubio N, Au H, Coulter GO, et al., 2021, Effect of graphene flake size on functionalisation: quantifying reaction extent and imaging locus with single Pt atom tags, Chemical Science, Vol: 12, Pages: 1-13, ISSN: 2041-6520
Here, the locus of functionalisation on graphene-related materials and the progress of the reaction is shown to depend strongly on the starting feedstock. Five characteristically different graphite sources were exfoliated and functionalized using a non-destructive chemical reduction method. These archetypical examples were compared via a model reaction, grafting dodecyl addends, evaluated with TGA-MS, XPS and Raman data. A general increase in grafting ratio (ranging from 1.1 wt% up to 25 wt%) and an improvement in grafting stoichiometry (C/R) were observed as flake radius decreased. Raman spectrum imaging of the functionalised natural flake graphite identified that grafting is directed towards flake edges. This behaviour was further corroborated, at atomistic resolution, by functionalising the graphene layers with bipyridine groups able to complex single platinum atoms. The distribution of these groups was then directly imaged using aberration-corrected HAADF-STEM. Platinum atoms were found to be homogeneously distributed across smaller graphenes; in contrast, a more heterogeneous distribution, with a predominance of edge grafting was observed for larger graphites. These observations show that grafting is directed towards flake edges, but not necessary at edge sites; the mechanism is attributed to the relative inaccessibility of the inner basal plane to reactive moieties, resulting in kinetically driven grafting nearer flake edges. This phenomenology may be relevant to a wide range of reactions on graphenes and other 2d materials.
Tapia-Ruiz N, Armstrong AR, Alptekin H, et al., 2021, 2021 roadmap for sodium-ion batteries, JOURNAL OF PHYSICS-ENERGY, Vol: 3, ISSN: 2515-7655
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- Citations: 113
Olsson E, Cottom J, Au H, et al., 2021, Investigating the effect of edge and basal plane surface functionalisation of carbonaceous anodes for alkali metal (Li/Na/K) ion batteries, CARBON, Vol: 177, Pages: 226-243, ISSN: 0008-6223
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- Citations: 13
Au H, Alptekin H, Jensen ACS, et al., 2021, A revised mechanistic model for sodium insertion in hard carbons (vol 13, pg 3469, 2020), ENERGY & ENVIRONMENTAL SCIENCE, Vol: 14, Pages: 3216-3216, ISSN: 1754-5692
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- Citations: 7
Robinson J, Xi K, Kumar RV, et al., 2021, 2021 roadmap on lithium sulfur batteries, Journal of Physics: Energy, Vol: 3, ISSN: 2515-7655
Batteries that extend performance beyond the intrinsic limits of Li-ion batteries are among the most important developments required to continue the revolution promised by electrochemical devices. Of these next-generation batteries, lithium sulfur (Li–S) chemistry is among the most commercially mature, with cells offering a substantial increase in gravimetric energy density, reduced costs and improved safety prospects. However, there remain outstanding issues to advance the commercial prospects of the technology and benefit from the economies of scale felt by Li-ion cells, including improving both the rate performance and longevity of cells. To address these challenges, the Faraday Institution, the UK's independent institute for electrochemical energy storage science and technology, launched the Lithium Sulfur Technology Accelerator (LiSTAR) programme in October 2019. This Roadmap, authored by researchers and partners of the LiSTAR programme, is intended to highlight the outstanding issues that must be addressed and provide an insight into the pathways towards solving them adopted by the LiSTAR consortium. In compiling this Roadmap we hope to aid the development of the wider Li–S research community, providing a guide for academia, industry, government and funding agencies in this important and rapidly developing research space.
Jensen ACS, Au H, Gartner S, et al., 2020, Solvation of NaPF<sub>6</sub> in Diglyme Solution for Battery Electrolytes, BATTERIES & SUPERCAPS, Vol: 3, Pages: 1306-1310
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- Citations: 11
Alptekin H, Au H, Jensen ACS, et al., 2020, Sodium Storage Mechanism Investigations through Structural Changes in Hard Carbons, ACS APPLIED ENERGY MATERIALS, Vol: 3, Pages: 9918-9927, ISSN: 2574-0962
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- Citations: 53
Au H, Alptekin H, Jensen ACS, et al., 2020, A revised mechanistic model for sodium insertion in hard carbons, Energy and Environmental Science, Vol: 13, Pages: 3469-3479, ISSN: 1754-5692
Hard carbons have shown considerable promise as anodes for emerging sodium-ion battery technologies. Current understanding of sodium-storage behaviour in hard carbons attributes capacity to filling of graphitic interlayers and pores, and adsorption at defects, although there is still considerable debate regarding the voltages at which these mechanisms occur. Here, ex situ23Na solid-state NMR and total scattering studies on a systematically tuned series of hard carbons revealed the formation of increasingly metallic sodium clusters in direct correlation to the growing pore size, occurring only in samples which exhibited a low voltage plateau. Combining experimental results with DFT calculations, we propose a revised mechanistic model in which sodium ions store first simultaneously and continuously at defects, within interlayers and on pore surfaces. Once these higher energy binding sites are filled, pore filling occurs during the plateau region, where the densely confined sodium takes on a greater degree of metallicity.
Nicolae SA, Au H, Modugno P, et al., 2020, Recent advances in hydrothermal carbonisation: from tailored carbon materials and biochemicals to applications and bioenergy, GREEN CHEMISTRY, Vol: 22, Pages: 4747-4800, ISSN: 1463-9262
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- Citations: 104
Clancy AJ, Au H, Rubio N, et al., 2020, Understanding and controlling the covalent functionalisation of graphene, Dalton Transactions, Vol: 49, Pages: 10308-10318, ISSN: 1477-9226
Chemical functionalisation is one of the most active areas of graphene research, motivated by fundamental science, the opportunities to adjust or supplement intrinsic properties, and the need to assemble materials for a broad array of applications. Historically, the primary consideration has been the degree of functionalisation but there is growing interest in understanding how and where modification occurs. Reactions may proceed preferentially at edges, defects, or on graphitic faces; they may be correlated, uncorrelated, or anti-correlated with previously grafted sites. A detailed collation of existing literature data indicates that steric effects play a strong role in limiting the extent of reaction. However, the pattern of functionalisation may have important effects on the resulting properties. This article addresses the unifying principles of current graphene functionalisation technologies, with emphasis on understanding and controlling the locus of functionalisation.
Au H, Rubio N, Buckley DJ, et al., 2020, Cover Feature: Thermal Decomposition of Ternary Sodium Graphite Intercalation Compounds (Chem. Eur. J. 29/2020), Chemistry – A European Journal, Vol: 26, Pages: 6291-6291, ISSN: 0947-6539
Au H, Rubio N, Buckley DJ, et al., 2020, Thermal decomposition of ternary sodium graphite intercalation compounds, Chemistry: A European Journal, Vol: 26, Pages: 6545-6553, ISSN: 0947-6539
Graphite intercalation compounds (GICs) are often used to produce exfoliated or functionalised graphene related materials (GRMs) in a specific solvent. This study explores the formation of the Na-tetrahydrofuran (THF)-GIC and a new ternary system based on dimethylacetamide (DMAc). Detailed comparisons of in situ temperature dependent XRD with TGA-MS and Raman measurements reveal a series of dynamic transformations during heating. Surprisingly, the bulk of the intercalation compound is stable under ambient conditions, trapped between the graphene sheets. The heating process drives a reorganisation of the solvent and Na molecules, then an evaporation of the solvent; however, the solvent loss is arrested by restacking of the graphene layers, leading to trapped solvent bubbles. Eventually, the bubbles rupture, releasing the remaining solvent and creating expanded graphite. These trapped dopants may provide useful property enhancements, but also potentially confound measurements of grafting efficiency in liquid-phase covalent functionalization experiments on 2D materials.
Bray JM, Doswell CL, Pavlovskaya GE, et al., 2020, Operando visualisation of battery chemistry in a sodium-ion battery by <SUP>23</SUP>Na magnetic resonance imaging, NATURE COMMUNICATIONS, Vol: 11
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- Citations: 47
Olsson E, Cottom J, Au H, et al., 2020, Elucidating the Effect of Planar Graphitic Layers and Cylindrical Pores on the Storage and Diffusion of Li, Na, and K in Carbon Materials, ADVANCED FUNCTIONAL MATERIALS, Vol: 30, ISSN: 1616-301X
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- Citations: 37
Ribadeneyra MC, Grogan L, Au H, et al., 2020, Lignin-derived electrospun freestanding carbons as alternative electrodes for redox flow batteries, CARBON, Vol: 157, Pages: 847-856, ISSN: 0008-6223
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- Citations: 28
Jensen ACS, Olsson E, Au H, et al., 2020, Local mobility in electrochemically inactive sodium in hard carbon anodes after the first cycle, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 8, Pages: 743-749, ISSN: 2050-7488
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- Citations: 25
Xie F, Xu Z, Jensen ACS, et al., 2019, Unveiling the role of hydrothermal carbon dots as anodes in sodium-ion batteries with ultrahigh initial coulombic efficiency, JOURNAL OF MATERIALS CHEMISTRY A, Vol: 7, Pages: 27567-27575, ISSN: 2050-7488
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- Citations: 60
Xu Z, Xie F, Wang J, et al., 2019, All-Cellulose-Based Quasi-Solid-State Sodium-Ion Hybrid Capacitors Enabled by Structural Hierarchy, ADVANCED FUNCTIONAL MATERIALS, Vol: 29, ISSN: 1616-301X
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- Citations: 63
Xie F, Xu Z, Jensen ACS, et al., 2019, Hard–Soft Carbon Composite Anodes with Synergistic Sodium Storage Performance, Advanced Functional Materials, Vol: 0, Pages: 1901072-1901072
Abstract A series of hard–soft carbon composite materials is produced from biomass and oil waste and applied as low-cost anodes for sodium-ion batteries to study the fundamentals behind the dependence of Na storage on their structural features. A good reversible capacity of 282 mAh g−1 is obtained at a current density of 30 mA g−1 with a high initial Coulombic efficiency of 80% at a carbonization temperature of only 1000 °C by adjusting the ratio of hard to soft carbon. The performance is superior to the pure hard or soft carbon anodes produced at the same temperatures. This synergy between hard and soft carbon resulting in an excellent performance is due to the blockage of some open pores in hard carbon by the soft carbon, which suppresses the solid electrolyte interface formation and increases the reversible sodium storage capacity.
Au H, Rubio N, Shaffer MSP, 2018, Brominated graphene as a versatile precursor for multifunctional grafting, Chemical Science, Vol: 9, Pages: 209-217, ISSN: 2041-6520
A non-destructive and versatile chemical reduction method was used to dissolve and subsequently brominate few-layer graphene sheets (FLGs); the direct covalent attachment of bromine to the graphene framework was demonstrated by X-ray photoelectron spectroscopy (XPS). The brominated few-layer graphenes (FLG-Br) provide a convenient, stable, liquid-phase precursor, suitable for the synthesis of a variety of directly functionalised graphenes. As an example, the FLG-Br species was used to initiate atom transfer radical polymerisation (ATRP), to obtain poly(methyl methacrylate) (PMMA)-grafted graphene (FLG-PMMA), which was six times more dispersible in acetone than controls. In addition, the FLG-Br is active for nucleophilic substitution reactions, as illustrated by the preparation of methoxypolyethylene glycol (mPEG)- and OH-substituted derivatives. The products were characterised by thermogravimetric analysis coupled with mass spectrometry (TGA-MS), XPS and Raman spectroscopy. Grafting ratios (GR) for these polymer-grafted materials varied between 6 and 25%; even at these GRs, all graphene derivatives showed increased solubility in organic solvents.
Rubio Carrero N, Au H, Leese HS, et al., 2017, Grafting from versus grafting to approaches for the functionalisation of graphene nanoplatelets with poly(methyl methacrylate), Macromolecules, Vol: 50, Pages: 7070-7079, ISSN: 0024-9297
Graphene nanoplatelets (GNP) were exfoliated using a nondestructive chemical reduction method and subsequently decorated with polymers using two different approaches: grafting from and grafting to. Poly(methyl methacrylate) (PMMA) with varying molecular weights was covalently attached to the GNP layers using both methods. The grafting ratios were higher (44.6% to 126.5%) for the grafting from approach compared to the grafting to approach (12.6% to 20.3%). The products were characterized using thermogravimetric analysis–mass spectrometry (TGA-MS), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), atomic force microscopy (AFM), and transmission electron microscopy (TEM). The grafting from products showed an increase in the grafting ratio and dispersibility in acetone with increasing monomer supply; on the other hand, due to steric effects, the grafting to products showed lower absolute grafting ratios and a decreasing trend with increasing polymer molecular weight. The excellent dispersibility of the grafting from functionalized graphene, 900 μg/mL in acetone, indicates an increased compatibility with the solvent and the potential to increase graphene reinforcement performance in nanocomposite applications.
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